Radiation absorption cell for optical testing apparatus



Feb. 24, 1948.

w. R. FLATFORD ET AL 2,436,511

RADIATION ABSORPTION CELL FOR OPTICAL TESTING APPARATUS Filed Sept. 7, 1945 3 Sheets-Sheet 1 LOWER CELL IN -Ill CELL IN "7 LATE DISTANCE EIIEEI 64 THOUSANDTHS LIGHT APERTURE PLATES 1W? 8 APART l2|\ '7 INVENTORS F. W. CRAWFORD W. R FLAT FORD 1948- w. R. FLATFORD ET AL 2,436,511

RADIATION ABSORPTION CELL FOR OPTICAL TESTING APPARATUS Filed Sept. 7, 1943 3 Sheets-Sheet 2 Feb. 24, 1948. w. R. FLATFORD El AL 2,436,511

RADIATION ABSORPTION CELL FOR OPTICAL TESTING APPARATUS Filed Sept. 7, 1943 3 Sheets-Sheet -3 s 'FYE ESEWFORD w. R. FLATFORD ma LC A'l'l'm FIG-l0 Patented Feb. 1948 RADIATION ABSORPTION CELL FOR OIPTL- CAL TESTING APPARATUS William R. Flatford and Francis W. Crawford,

Bartlesville, kla., assignors to Phillips Petroleum Company, a corporation of Delaware Application September 7, 1943, Serial No. 501,506

4 Claims. (Cl. 88-14) This invention relates to spectrophotometry and it has particular relation to apparatus used in holding and manipulating cells containing fluids to be tested and comparison cells.

It has been found that diilerent fluids respond differently to the transmission of light of difierent wave lengths. For example, water absorbs some light in the infra-red but transmits visual light freely whereas benzene absorbs the light heavily in the ultra-violet end of the spectrum. Each chemical substance has an individual response and by plotting absorption curves with light wave length same axis and percent absorption as the other axis the exact chemical identity of the substance being tested may be discovered although no other method might reveal what it is. The absorption spectrum or the Raman spectrum may be used. Mixtures of two compounds too close in nature to be chemically or physically separated may have their percentages of respective components revealed by spectrophotometry.

The devices of the prior art have proved to be unequal to the problem of dealing with an opaque liquid, or one having a relatively low boiling point especially those of a hydrocarbon nature. The usual square quartz cell is too thick for opaque liquids and they have to be diluted with a suitable solvent. This dilution with the solvent is too uncertain as the small quantity involved makes it diiiicult to measure the exact percentage of dilution and the purity of the solvent must be carefully tested. With a volatile liquid the material may be lost before it can be analyzed. No simple apparatus for handling gases or liquids exists. If the Baly tube of the prior art is used, the rubber seal is soon destroyed by the compounds being tested, such as hydrocarbons, and small parts of the rubber seal will dissolve and enter the test chamber in the tube and spoil the accuracy of the test results, or if the hydrocarbon must be con-' flned under pressure there are difliculties with leakage as the Baly tube will not retain liquids under any substantial pressure.

It is also known that the absorption of a fluid varies with the pressure and temperature of the fluid, so control of the pressure as well as the temperature is regarded as important.

One object of our invention is to overcome these objections to the prior art by providing apparatus which will handle all types of fluids in its absorption cells.

Another object is to provide a practical instrument to solve practical problems in the industrial application of spectrophotometry to analyses for plant control.

Another object is to provide a set of absorption cells that can be used efiectively with minimum chance for errors by personnel not so highly skilled as graduate technicians without sacrifice of precision.

Another object is to provide apparatus by which the operator will be able to analyze either liquid or gaseous substances at will without loss of time.

Another object is to provide a cell in which the pressure may be varied so that volatile fluids may be kept in liquid phase, or a partial vacuum created over the liquid, or the fluid may be tested as a compressed or a rarefied gas.

Numerous other objects and advantages will be apparent to those skilled in the art. upon reading the following specification, studying the drawings and reading over the claims of this application.

In the drawings:

Figure 1 is an elevational view of one side of our absorption cell magazine showing the controls and with the fluid supply pipes broken away.

Figure 2 is a perspective view of our absorption cell magazine with the telescoping absorption tube in operative position.

, Figure 3 .is a view similar to Figure 2 in which the vertically sliding fixed volume cells are in operative position, and with the hatch removed to give access to these cells.

Figure 4 is a cross sectional view taken along a vertical plane through the axis of the telescoping absorption tube, with the exception that substantially the lower front quarter of the tube is not in section, parts being broken away.

Figure 5 is a perspective view showing the first step in building up the liquid cell.

Figure 6 is a perspective view showing the first step in assembling the cell.

Figure 7 is a perspective view showing the same cell as Figures 5 and 6 after it is fully assembled.

Figure 8 is a perspective view showing two of the cells detachably secured together as a unit.

Figure 9 is a a perspective view showing the assembly and operation of the liquid cells with all unrelated parts removed for clarity.

Figur 10 is a cross sectional view taken just inside the far wall of Figure 2 looking toward the near wall and showing the relationship of parts with a special reference to the light obscuring triangle and the rack and pinion for operating the same.

Figure 11 is a fragmentary view showing the light obscuring triangle and its relation to the light transmitting orifice.

a lead amalgam around its periphery.

it goes to a photometer (such as the photometer supplied with the Beckman ultra-violet spectrophotometer) When the absorption cell 23 is held still and handle 24 is pulled, the apparatus moves from the position of Figure 2 to that of Figure 3 and in that case. the light entering orifice 20 passes through whichever liquid cell 25 in Figure 9 is positioned in front of the orifice, the light passing through hole 23 in the back of the cell and out through orifice 22 to the photometer (not shown).

Describing the apparatus in the position of Figure 2, attention is directed to Figure 4 in which a telescoping absorption cell 2| of a particularly novel and valuable construction forms a part of our invention. This cell is adapted to handle gases or liquids under pressure or vacuum.

Case 23 is a box-like structure having like orifices 23 and 22 formed therein and having horizontal tracks 21 placed above and below the oriflce 20; the housing 23 being chamfered to form a channel 23. Sliding horizontally in channel 23 and guided by tracks 21 is a supporting frame arm 29 on which the tube 2| is seated. The frame arm 29 is provided with a threaded opening 3| which receives the threaded nose 32 of the tube 2|, the tube being screwed up firmly against the arm 29. The tube 2| is provided with upper and lower fluid conducting tubes 33 so that liquids, vapors and gases may be forced into space 34 and held in a liquid state therein if desired. Valves I23 and I29 control the flow in tubes 33.

The nose 32 is provided with internal screw threads 33 into which a ferrule sleeve 31 may be screwed to hold quartz plate 33 in place. Quartz plate 33 is frusto-conical in shape and has a band of lead amalgam 33 around its periphery sealing it tothe tube 2|.

A movable tube 4| is similarly provided with a quartz window 33' of frusto-conical shape having Window 33' is held in tube 4| by concentric internal tube 42 and tube 42 is secured in tube 4| by screw sleeve ferrule 43. Sleeves 31 and 43 are provided with engagement slots 44 by which they may be adjusted. I

The seal for chamber 34 between tube 2| and tube 4| is completed by means of metallic bellows 43 which is made out of thin steel. We may employ a 0.005 inch "Rex" bellows made of S. A. E. 18-8 steel, but any suitablebellows may be used. A metal bellows is preferred but other types of material not attacked by the organic liquids tested could be employed. Bellows 43 is welded to'rings 41 and 43. Ring 41 fits 'snugly against tube 2| and ring 41 is provided with small triangular'apertures 49 to allow passage of fluid between the ring and tube 4|. Ring 41 is secured to tube 2| by screws ii, a lead amalgam gasket 52 supplying a seal between the parts. A similar fluid seal between ring 43 and tube 4| is provided by lead amalgam gasket 33 and screws 34. Screws 34 have the additional function of securing a drive sleeve 33 to tube 4|. Drive sleeve .33 is provided with threads 51. A shaft 33 has a very stee pitched worm 33 keyed thereto and tion counter 34 is provided with a gear 33' on its drive shaft meshing with gear 33. By aproper adjustment of gear sizes the numbers on the revolution counter may be made to be exact units of distance between the quartz plates 33 and 33. We prefer. to have this plate distance measured in thousandths of an inch but of courseany units may be employed.

Sleeve 3| is secured to a screw sleeve 31 by screws 33. The screw sleeve 31 has internal screw threads complementary to threads 31. Tube 2| being held from rotation by arm 23 and being connected non-rotatably to tube 4| by bellows 43 it. will be seen that rotation of rod 33 will turn sleeves BI and 6] and force sleeve 53 and with it tube 4| (which is secured to sleeve 53 by screws 54) in and out varying the distance between windows 33 and 38'.

Rods 39 and 1| are rotatably supported in the back wall 12 of Figure 4. These rods will be described later. 4

In Figures 5 to.8 is shown the preferred method of construction of our preferred liquid cells. 7

In Figure 5, two quartz plates 13 and 14 are spaced the desired distance apart and the front and rear adjacent edges are fused together. While the size of the cells is not part of the invention we may use quartz windows each /g inch by /3 inch by 1 inch. In this manner a square tubular cell 13 is created having an internal space 13, the thickness of the quartz plates 13 and 14 being preferably the same as plates 33 and 33' of Figure 4.

Turning to Figure 6, we assemble the liquid cells by placing the quartz tube 13 in the angle of metal angle 3| and bringing up a metal plate 32-. Plate 32 and end 33 of angle 3| both have oval holes 34 therein and the light passes through these holes 34 and through the quartz 13 in traversing the instrument, 7

Tube 13 is clamped between the plates 32 and 33 by screws 33.

The top and bottom of angle 3|, plate 32 and quartz cell 13 are then ground off to a smooth flat surface and lead amalgam is applied to these top and bottom ground surfaces. As shown in Figure '1, end plates 31 are then secured by means of screws 33 to the top and bottomof the cells and are sealed thereto by the lead amalgam. The top end plate 31 is provided with a screw threaded opening 39 which is directly over opening 19 in cell 13. Opening 33 is closed by a screw threaded plug 9|. g

Figure 8 shows the rear view of the cells as viewed in Figures 6 and '1. Two liquid cells 92 and92' have been placed on top of each other. Plate 3| is provided with a vertical groove 32' which has a horizontal branch 33'. Grooves 32' and 33' will be explained later. The back of plate 3| also has a pin 34' projecting therefrom and a link member 33' is screwed'to plate 3| by screw drives sleeve 3| by means of worm wheel teeth bottom to provide a guide as will be described later.

Figure 9 shows how the cells 92 and 92' are assembled in the liquid cell portion of the apparatus. Ann 29 is provided with a window which is positioned in alignment with orifice 20 when the apparatus is in the position shown in Figure 3. As shown in Figure 9, cell 92 is in position and groove 93 is guided on rod 94 secured in guide groove 96. The cells 92 and 92' are held up against guide rod 94 and guide strip 91 by sled runner 98 which is urged toward plate 12 by spring 99. Spring 99 is secured to plate 12 by block IN and the illustrated screws.

Rod 69 is non-rotatably secured to crank arm I02 and crank arm I02 has a pin I03 shown in dotted lines. As crank arm I02 is raised, pin I03 will move in slot 83' and carry the cells 92 and 92' upward until cell 92' is centered over orifice 20.

In Figure 10, shaft 1| has non-rotatably mounted thereon a spur gear I03 engaged with rack I04. When rod 1| is'tumed, rack I04 moves up and down. Mounted on rack I04is a triangular shaped opaque sheet metal" wedge I06 and as shown in Figure 11 as rack I04 rises wedge I08 cuts oil the light passing through orifice 20. In Figure 1 the ends of pipes 33 are shown as coming down between housing 23 and instrument panel plate I01. Space for these pipes 33 can be provided by making notches in housing 23, plate I01 or both. The various controls shown on the face of plate I01 are connected to the instrumentalities described as follows:

Crank arm I08 is keyed to rod 69 and may contain a spring pressed detent I09. An operating knob III is provided on the crank I08 and an are I I2 may be secured to panel I01 by screws. The are II2 may be provided with recesses H3, H4 and H6 and stops H1 and H8 giving three positions to be described later.

The Veeder counter 64 reads through a hole in plate I01. Handle 24 is provided on the plate I01 for pulling the plate out. Rod H is nonrotatably secured to knob II9, which has nonrotatably secured to it a pointer I2I and a scale may be engraved on plate- I01 as shown to indicate the position of wedge I06 of Figure 11.

Rod 58 is non-rotatably secured to crank arm I22 having an operating handle I23 thereon.

A hatchway I24 is provided in the top of housing 23 so that accessto cells 92 and 92' may be provided. The hatchway is covered by a hatchway cover I26 which may be tapered or have some other construction to hold it flush with the top of 23, and it may be provided with a knob I21 for a handle.

The operation of the apparatus is as follows:

When the apparatus is in the position shown in Figure 2, the telescopic cell 2| of Figure 4 is lined up with apertures 20 and 22 so that the light passing to the photometer from the spectrum producer passes through the telescopic cell. We preferably use any liquid or gas in the telescopic cell without using any solvents to decrease its opacity as the thickness of the fluid can be varied by turning handle I23 and the distance between plates 38 and 38' may be read in thousandths of an inch at 84. The liquid or gas must be one that may be volatilized or blown out of the telescopic tube by warm air. As a comparison cell, the telescopic tube might be used while empty but as the reading on the photometer may vary from time to time, we prefer to shift the device to the position shown in Figure 3 and use an empty liquid cell 92 (the quartz walls 13 and 14 of which are the same optical thicknes as plates 38 and 38' of the tube 2|) as a comparison cell.

When the comparison reading is made the device can be shifted quickly back from the position of Figure 3 to the position of Figure 2 and readings then taken with the telescopic tube 2I.

When a, liquid which does not vaporize readily is to be tested, we prefer to use the liquid cells 92 and 92'. One 01. these may be empty or may contain water or a normal paramn hydrocarbon if ultra-violet light is being employed or carbon tetrachloride if infra-red light is employed. These standards of comparison set forth in this paragraph are all old.

When lever I08 is in the position shown in Figure 1, and the device is in the position shown in Figure 3, the upper cell 92 will transmit the light from orifice 20. When lever I08 is moved so that detent I08 enters notch II4, the lower cell 92' will be moved into that position and receive light from orifice 20. Figure 9 shows that pin I03 runs close to slot 82' in these positions,

so by moving lever I08 a little further to notch I I6 liquid cells 92 and .92 become released, as pin I03'is now in slot 82', and the operator can lift the two cells out of hatchway I24 the cells being secured together by link 86' of Figure 8.

Pipes 33 are provided with valves I28 and I29. Due to the strong construction utilizing the metal bellows 46 a considerable amount of pressure may be maintained in space 34 by forcing fluids into 33. In this way substances which would be volatile at a certain temperature may be kept at a temperature where they will be in liquid phase and thus be tested in our" apparatus. And substances normally in the liquid phase can have the atmospheric pressure relieved so that they become gaseous for the purposes of the test.

Let the intensity of the light through the comparison cell be 10 and the intensity of light through the sample containing cell be L then the percent transmission T of the sample is:

It will now be apparent that we have accomplished the objects of our invention by providing a novel and useful construction and combination of parts. Obviously numerous changes in design and construction of parts, such as the use of other gaskets and sealing agents than lead amalgam, or the use of difierent gears than those shown, do not avoid the scope of our invention, the invention being limited in scope only by the following claims.

Having described our invention, we claim:

1. In an optical testing apparatus, a radiation absorption cell comprising in combination an outer cylinder, a first transparent plate closing one end of the outer cylinder, an inner cylinder in telescoping relationship with the outer cylinder, a second transparent plate closing the corresponding end of the inner cylinder, a bellows sleeve connecting the opposite end of the inner cylinder to the outer cylinder, whereby an expansible fluidtight chamber is formed with relatively movable transparent walls, means to move the plates together and apart, means to supply fluid to the chamber under suitable absolute pressure and means to indicate the distance between the plates.

2. In an optical testing apparatus, a radiation absorption cell comprising in combination an outer cylinder, a first transparent plate closing one aesam 'end of the outer cylinder, an inner cylinderin telescoping relationship with the outer cylinder,

a second transparent plate closing the corresponding end of the inner cylinder, a bellows sleeve connecting the opposite end of the inner cylinder to the outer cylinder, whereby an expansible fluidtight chamber isformed with relatively movable transparent walls, means to move the plates together and apart and means to supply fluid to the chamber under suitable pressure.

8. In an optical testing apparatus, a radiation absorption cell comprising in combination an out- 'er cylinder, an internally threaded nut rotatably mounted on said outer cylinder to rotate about the axis of said outer cylinder, a first transparent plate closing oneend of the outer cylinder, an intermediate externally screw threaded cylinder extending into said outer cylinder and threaded into said nut, an inner cylinder secured inside said intermediate cylindena second transparent plate closing one end 01 said inner cylinder, and

a metal bellows disposed between said intermeder and said inner cylinder with the ends of said diate cylinder and said inner cylinder with the I ends of said bellows hermetically sealed to said outer and inner cylinders respectively whereby an e'xpansible fluidtight chamber is formed with relatively movable transparent walls, means to supply fluid to the chamber under suitable pressure, gearing to rotate said nut, and a counter geared to said nut, to indicate the distance between said 30 plates. c I

4. In an optical testing apparatus, a radiation 4 absorption cell comprising in combination an outbellows hermetically sealed to said outer and inner cylinders respectively whereby an expansible fiuidtight chamber is formed with relatively movable transparent walls and means to supply fluid to the chamber under suitable pressure.

WILLIAM R. FLA'I'EOBD. FRANCIS W. CRAWFORD.

REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PA'lI'ENTS Number Name Date 1,954,925 EXton Apr. 17, 1934 2,258,073 Stevens Oct. 7, 1941 2,051,317 Sheard et al Aug. 18, 1936' FOREIGN PATENTS Number Country Date 128,528 Austria June 10, 1932 

